Method for controlling pressure in a hydraulic circuit

ABSTRACT

The invention is based on an apparatus ( 10 ) for regulating the pressure in a hydraulic circuit that comprises an electrically triggerable pressure-control valve ( 12 ), a receptacle device ( 14 ) in which the pressure-control valve ( 12 ) is installed, and means ( 54, 64 ) for damping pressure pulsations. In order to save space, simplify the manufacture of the receptacle device ( 14 ), and save additional holding elements, it is proposed according to the invention that the means ( 54, 64 ) for damping pressure pulsations be designed as integral components of the pressure-control valve ( 12 ).

RELATED ART

[0001] The invention is based on an apparatus for regulating thepressure in a hydraulic circuit according to the definition of thespecies in claim 1. Apparatuses of this type are used in automaticgearboxes of motor vehicles in particular, to trigger gear changes viacontrol of the pressure level, for example.

[0002] For this, known apparatuses comprise an electrically triggerablepressure-control valve, like the one made known previously in DE 197 33660 A, for example. This pressure-control valve comprises a solenoidpart constructed in conventional fashion having coil, coil core, fluxconcentrating element and armature, and a hydraulic part havingmechanical linkage with the solenoid part. In the hydraulic part, ashutoff element able to be acted upon by the armature controls the flowof hydraulic fluid between inlet passages, working passages, and returnpassages.

[0003] This known pressure-control valve can be installed with itshydraulic part in a receptacle device—a “hydraulic control block”—inwhich recesses are provided that direct hydraulic fluid and are matchedto the corresponding passages of the pressure-control valve. Appropriatedevices are provided to dampen pressure pulsations, which can occurduring operation of the pressure-control valve in the recess matched tothe working passage. These devices are attached in the receptacle deviceas separate components.

[0004] The separate arrangement of the damping devices described isdisadvantageous, because it makes a large number of holding elementsnecessary, takes up a relatively large space, generates additional work,and is costly to install.

ADVANTAGES OF THE INVENTION

[0005] In contrast, an apparatus according to the invention forcontrolling the pressure in a hydraulic circuit having the features ofclaim 1 has the advantage that the means for damping pressure pulsationsare an integral component of the pressure-control valve. This savesspace, simplies the manufacture of the receptacle device, and makesseparate holding elements superfluous, without making assembly of thepressure-control valve itself more difficult. The pressure pulsationsare damped by means of the invention directly at the site of origin,which greatly improves the damping effect. Due to the damping, thepressure/flow characteristic of a pressure-control valve can be keptwithin narrow tolerances under nearly all operating conditions.Additionally, the prevention of pressure pulsations has a positiveeffect on the wearing behavior of the pressure-control valve, so thatits service life is extended.

[0006] Further advantages or advantageous further developments of theinvention result from the subclaims and the description.

[0007] The devices can be integrally molded on one of the sealingelements of the pressure-control valve particularly easily, so that thetotal number of components to be obstructed remains unchanged. Thedevices, together with the housing of the pressure-control valve,enclose a damping chamber having a variable volume. Its damping behaviorcan be varied by means of vents to the recess of the receptacle devicematched to the return passage of the pressure-control valve inaccordance with the specific case of application. This vent can also bedesigned in advantageous fashion as throttling point.

BRIEF DESCRIPTION OF THE DRAWING

[0008] Exemplary embodiments of the invention are presented in thedrawing and explained in greater detail in the following description.

[0009]FIGS. 1 and 2 are sectional diagrams of a longitudinal section oftwo diifferent exemplary embodiments of an apparatus according to theinvention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0010] Each of the apparatuses for controlling the pressure in ahydraulic circuit labelled in FIGS. 1 and 2 with the position number 10comprises an electronically triggerable pressure-control valve 12 and areceptacle device 14 in which this pressure-control valve 12 with itshydraulic part 18 is installed. In addition to its hydraulic part 18,the pressure-control valve 12 also comprises a solenoid part 16.Comprising this solenoid part 16, an electrically triggerable,hollow-cylindrical coil 20, a moveably guided armature 22, and a fluxconcentrating element 24 surrounding the coil on its circumference areshown in sections. The armature 22 comprises a section 22 a projectinginto the interior of the coil 20, a collar 22 b adjoining this andspanning the front side of the coil 20, and a neck 22 c in axialextension of this collar 22 b. A through hole 26 extends through thecenter of the armature 22, into which a pushrod 28 is pressed in theregion of the neck 22 c. This pushrod 28 penetrates a guide 30 providedin the hydraulic part 18 and designed in the shape of an eyelet andactuates a shutoff element 32 with its end, the outer diameter of whichis tapered. The shutoff element 32 is designed in the shape of a balland bears against the pushrod 28 as a result of hydraulically-inducedforces of flow and pressure. The shutoff element 32 serves to control afirst valve seat 34 formed in the hydraulic part 18, the inner diameterof which is greater than the outer diameter of the pushrod 28. Anannular orifice therefore exists between pushrod 28 and valve seat 34,through which hydraulic fluid can flow when the valve seat 34 is opened.

[0011] A second valve seat 36 of the hydraulic part 18 is formed on aperforated plate 38 that is injected, facing the solenoid part 16, intothe hydraulic part 18. This perforated plate 38 is controlled by thefront end of the neck 22 c and lies in alignment with the first valveseat 34. In the non-energized starting position of the armature 22shown, the first valve seat 34 is open and the second valve seat 36 isclosed. In addition, the armature 22 is moved into the starting positionshown by a return device, e.g., in the form of a spring (not shown).Current is not supplied to the coil 20.

[0012] The hydraulic part 18 is firmly connected to the solenoid part 16of the pressure-control valve 12. This solenoid part 16 is manufacturedusing injection molding technology, preferably using plastic, andcomprises an injected holding element 40. The latter is designed in theshape of a sleeve, and its diameter is offset repeatedly. Anon-extrusion-coated part of the holding element 40 projects over thehydraulic part 18 and firmly encloses the flux concentrating element 24of the solenoid part 16. A second guide 42 for the armature 22 islocated at the smallest diameter of the holding element 40 lying insidethe hydraulic part 18. At the same time, this guide 42 forms an end stopfor limiting the up-and-down motion of the armature 22.

[0013] A continuous, longitudinal recess 44 extending in the directionof its longitudinal axis is provided at the hydraulic part 18 fordirecting hydraulic fluid, into which two transverse passages 46, 48,one extending over the top of the other, empty at right angles. Thefirst transverse passage 46 facing the solenoid part 16 is designed inthe fashion of a blind hole and forms the return passage R of thepressure-control valve 12, while the transverse passage 48 opposite tothe solenoid part 16 penetrates the hydraulic part 18 and acts as theworking passage A. The front end of the longitudinal recess 44 forms aninlet passage 50—labelled “P”—for the hydraulic part 18. The latterempties into the working passage A when the valve seat 34 is open, whilethe hydraulic passage between the working passage A and the returnpassage R is interrupted. Using an electrically triggered coil 20, theserelationships are reversed accordingly, that is, a hydraulic connectionexists between the return passage R and the working passage A, while theinlet passage P is blocked.

[0014] Recesses 46′, 48′, 50′ of the receptacle device 14 are matched tothe passages 46, 48, 50 of the pressure-control valve 12. Sealingelements 52 and 54 are provided on the circumference of the hydraulicpart 18 for the mutual sealing of these recesses 46′, 48′, 50′. Thefirst sealing element 52 separating the inlet passage P from the workingpassage A is a conventional O-ring that is held on a filter cage 56. Theannular filter cage 46 manufactured out of plastic that is resistant tohydraulic fluid is slid onto the end section of the hydraulic part 18and comprises a filter fabric that covers the opening cross section ofthe working passage A. This filters contaminants out of the hydraulicfluid flowing out of the working passage A to a hydraulic consumingdevice (not shown).

[0015] The second sealing element 54 serving to separate the workingpasage A from the return passage R is composed, according to theinvention, of an O-ring cross section 58 having sealing function and anintegrally molded diaphragm 60 having a thickened end 62. The sealingelement 54 is also produced out of elastic material resistant tohydraulic fluid having good impermeability properties, so that thediaphragm 60 can be stretched using its thickened end 62 between thefilter cage 56 and a shoulder of the hydraulic part 18 on the housingside. An annular pressure chamber 64 closed off from the surroundings isthereby produced between the diaphragm 60 and the housing of thehydraulic part 18. The interior space of this pressure chamber 64 isfilled with air.

[0016] In the installed stated of the pressure-control valve 12 shown,the diaphragm 60 is located in the recess 48′ of the receptacle device14 matched to the working passage A. Due to its malleability and,therefore, the variability of the volume of the pressure chamber 64enclosed by it, the latter is capable of damping pressure pulsationsthat can occur in the working passage 48 and the connected recess 48′.Using the sealing element 54 designed according to the invention,therefore, a hydraulic capacity is created in the working passage Awithout appreciably changing the space required therefore, the number ofindividual parts or the installation expenditure required. An increasein the stiffness of the diaphragm 60 could be realized, if necessary, bymeans of a spring element (not shown) that can be located in theinterior space of the pressure chamber 64. By varying the springelements used, a damping characteristic adapted to the specific case ofapplication could be achieved.

[0017] The second exemplary embodiment according to FIG. 1 differs fromthe first exemplary embodiment by the fact that the pressure chamber60—the volume of which can be changed-is connected to the recess 46′ ofthe receptacle device 14 matched to the return passage R of thepressure-control valve 12 via a vent 66. As a further actuating variableon the damping characteristic, the vent 66 can be designed as dampingthrottle. It would also be feasible to provide a plurality of such vents66 or to divide the pressure chamber 64 into multiple sections.

[0018] Further-reaching changes or additions to the exemplaryembodiments are possible, of course, without deviating from the basicidea of the invention. A {fraction (3/2)} directional-controlproportioning valve is preferably used as the pressure-control valve 12,the armature 22 of which can be moved into any intermediate position bythe solenoid part 16. Operating positions can also be described in whichboth valve seats 34 and 36 are open simultaneously.

What is claimed is:
 1. An apparatus (10) for regulating the pressure ina hydraulic circuit having an electrically triggerable pressure-controlvalve (12) that comprises a solenoid part (16) having an electricallytriggerable coil (20), a moveably guided armature (22) and a hydraulicpart (18) coupled to the solenoid part (16), in which a shutoff element(32) able to be acted upon by the armature (22) controls the flow ofhydraulic fluid between at least one working passage (48) and a returnpassage (46), and having means (54, 64) for damping pressure pulsationsin the working passage (48), wherein the means (54, 64) are an integralcomponent of the pressure-control valve (12) and, in interaction withits housing, limit at least one pressure chamber (64) located on thecircumference and having a variable volume.
 2. The apparatus accordingto claim 1, wherein at least one wall of the pressure chamber (64) isformed by an elastically malleable diaphragm (60).
 3. The apparatusaccording to claim 2, wherein the diaphragm (60) is integrally molded ona sealing element (54) of the pressure-control valve (12).
 4. Theapparatus according to claim 3, wherein the end of the diaphragm (60)located at a distance from the sealing element (54) is fixable withaxial separation from this sealing element (54) on the circumference ofthe pressure-control valve (12).
 5. The apparatus according to claim 3or 4, wherein the sealing element (54) forming the diaphragm (60) sealsoff the return passage (46) and the working passage (48) from eachother.
 6. The apparatus according to one of the claims 1 through 5,wherein the pressure chamber (64) is hermetically sealed off from thesurroundings.
 7. The apparatus according to one of the claims 1 through5, wherein the pressure chamber (64) is connected to the return passage(46) by means of a vent (66).
 8. The apparatus according to claim 7,wherein the vent (66) is outfitted with a damping throttle.
 9. Theapparatus according to one of the claims 1 through 8, wherein thepressure-control valve (12) is designed as a hydraulic {fraction (3/2)}directional-control proportioning valve that comprises an inlet passage(50) in addition to the working passage (48) and the return passage(46).
 10. A control device for an automatic gearbox of a motor vehiclehaving an apparatus (10) according to one of the claims 1 through 9.